The present invention generally relates to an electric hair cutting device such as a trimmer or a hair clipper. More particularly, the present invention relates to an electric hair cutting device having a detachable and rotatable blade assembly.
Electric hair trimmers or clippers are commonly used by stylists, barbers, or individuals for styling hair, and typically include a handle having a housing for enclosing a motor and a blade assembly associated with the handle. The blade assembly is generally fixed to the handle at a certain orientation for receiving driving power from the motor. A bladeset in the blade assembly includes a stationary blade and a moving blade reciprocating laterally and substantially parallel relative to the stationary blade to provide a scissors-type cutting action.
One problem incurred when using current hair trimmers is orienting the trimmer to reach areas that are difficult to cut, such as behind the ears or the nape of the neck. In these situations, the entire trimmer must generally be maneuvered to change the orientation of the blades and reach the area to be cut. Such movement is awkward, and often causes discomfort to the user's wrist or hand after continued use, and also decreases the accuracy and/or efficiency of the trimmer because the blades may not be entirely in contact with the cutting area.
To attempt to resolve this problem, hair trimmers were developed having heads rotatable relative to the handle, such as commonly owned U.S. Pat. No. 5,970,616 to Wahl et al., which discloses a hair trimmer having a lighted rotating head. In Wahl, a cutting surface extends at an angle from a blade housing that is rotatable with respect to a main body of the hair trimmer. An interface plane is defined between the main body and the blade housing, and is arranged at an oblique angle relative to a longitudinal axis of the main body. Although this arrangement provides the user with added comfort, especially during beard trimming alternately using both hands, due to the angle of the blade housing relative to the longitudinal axis of the main body, it can still be difficult to efficiently reach and cut other hard to trim areas.
To address this problem, a hair trimmer with a rotatable and pivotable blade assembly was developed, seen in commonly-owned U.S. Pat. Nos. 5,579,581 and 5,606,799 to Melton. In Melton, a handle portion is detachably connected to a blade assembly by a ball-and-socket connection, allowing the blade assembly to be easily detached without the need for additional tools. The ball-and-socket connection enables the blade assembly to rotate relative to the handle portion through 360°, as well as pivoting in a wide variety of positions, enabling the user to cut hard to reach areas. However, Melton does not provide a mechanism that secures or locks the blade assembly in a desired position. Accordingly, the blade assembly can move from the desired rotatable position during use, causing inaccurate trimming.
Yet another design criterion of current hair trimmers with rotatable blade assemblies is imbalance caused by operational vibrations. One source of imbalance is the use of only one attachment or locking point holding the blade assembly in position. Such imbalance reduces the cutting accuracy of the trimmer, and also causes user discomfort because of the resulting vibrations.
Accordingly, there is a need for an improved hair trimmer having a blade assembly that is rotatable and detachable through 360° relative to the handle, and which addresses the above-listed design factors. Further, there is a need for an improved hair trimmer that provides a stable and balanced attachment between the blade assembly and handle, and reduces the vibrations experienced by the user during operation.